This grant application responds to the program announcement for studies of Epidemiology and Prevention in Alcohol Research (PA-18-391) calling for exploratory and developmental research issued by the National Institute on Alcohol Abuse and Alcoholism. The application proposes a secondary analysis of data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) to examine when and why Asian Americans engage in heavy alcohol and tobacco use and co-use across the lifecourse (from ages 12-43). In addition to exploring patterns of alcohol and tobacco co-use, we will extend the investigation of alcohol and tobacco use into adulthood with a focus on risk and resiliency factors relevant to the Asian American experience. First, the study will provide descriptions of longitudinal trends of elevated and sustained alcohol and tobacco use and co-use from adolescence to adulthood. Then, we will identify risk and resiliency predictors at multiple levels (i.e., individual, family, interpersonal, and neighborhood) for Asian Americans that are associated with sustained alcohol and tobacco use and co-use over time. We innovate by employing time-varying effect modeling to determine specific ages and developmental periods for informing preventive interventions, setting us apart from extant developmental research. The third analyses will use moderated mediation to address how contextual risks may influence behavior by ascertaining whether depression helps to explain associations of risk exposures on alcohol and tobacco use and co-use. We will examine whether protective factors at multiple levels buffer the deleterious effects of the contexts with which individuals interact. Finally, we replicate key analyses to: 1) compare Asian Americans to major US racial/ethnic groups (non-Hispanics Whites, Hispanics, and Blacks) to determine whether mechanisms are unique to this population or common across groups, and 2) assess for Asian American subgroup differences (by gender, nativity, and ethnicity) to address within-group heterogeneity in alcohol and tobacco use patterns. The objectives of this project are directly relevant to the NIH?s current strategic plan to generate knowledge for intervention development to reduce health disparities related to alcohol and tobacco. This exploratory study will inform prevention science by permitting the identification of specific contexts and mechanisms within certain developmental periods relevant to sustained alcohol and tobacco use and co-use among Asian Americans. The study will also build on prior research by extending the lifecourse examination of heavy alcohol and tobacco use into adulthood and by focusing on co-use in Asian Americans. As noted in the program announcement, this research is critical for establishing a knowledge base in developing culturally relevant preventive interventions to address use and misuse in diverse communities. Future projects will be designed to help translate the study findings into community-based, multilevel interventions for at-risk Asian Americans within specific contexts.